Human Potential

• Humans who swallow eucalyptus leaves may suffer from serious symptoms such as nausea, vomiting, diarrhea and coma upon ingestion, states North Carolina State University. Severe symptoms occur with eating large quantities of the leaves. Handling the eucalyptus leaf can cause skin irritation, redness and burning.
  
  

Animal Potential

• According to Vet Info.com, the eucalyptus leaf is one of the most poisonous plants for dogs. Dogs that ingest this leaf may suffer from symptoms such as depression, excessive salivation, lethargy, diarrhea and vomiting. Cats and horses also develop symptoms of plant poisoning, if they eat eucalyptus leaves, warns the ASPCA.
  
  

Prevention/Solution

• Ingestion of the eucalyptus leaf may require an evaluation by a doctor or veterinarian. Be certain to take a piece of the plant with you for identification purposes; but remember that handling eucalyptus leaves can cause skin irritation.